An automated machine, British in origin (5)
I believe the answer is:
robot
'an automated machine' is the definition.
(I've seen this before)
'british in origin' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'in' means one lot of letters goes inside another.
'origin' becomes 'root' (synonyms).
'b' inserted into 'root' is 'ROBOT'.
(Other definitions for robot that I've seen before include "Factory worker, perhaps" , "Automatic machine" , "Automation" , "Lifelike machine" , "Programmable machine" .)